What is the theme in Digital Fortress by Dan Brown?

The main theme of this novel deals with the controversial issue of national security and an individual's right to privacy. Susan Fletcher works as a cryptographer for the NSA, a government organization responsible for intercepting intelligence and protecting the citizens of the United States. Susan believes that she works for an organization that has the country's best interests at heart. She does not believe that the NSA would ever use its power against the American people. Susan agrees with her boss, Commander Trevor Strathmore, that the NSA should be permitted total access to all communication in order to protect the country from terrorist attacks.